Fourth Kanto War
by Danny vs A Month
Summary: Rentaro finally has the chance to save all of his friends. Unfortunately, Hiruko Kagetane has decided to have one final go at the Tokyo Area. Unsure on pairing.
1. Chapter 1

I do not own Black Bullet or any of the characters. So, I know it's nor a very popular category but I decided to try it. Also, I'm only watching the anime and am only at the point where the 32 monolith is destroyed. Don't know anything about the battle and haven't started it yet. And the wiki is useless because it doesn't follow the anime.

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New Assignment

It had been about a year since the Third Kanto War. Since then, things had been surprisingly peaceful. Of course, Rentaro was very far from unstressed. After the war, very little had changed with the Cursed Children, the Gastrea had continued to attack, and most importantly, Tina and Enju's corrosion rates were both nearly at fifty percent. Enju had been sidelined with a rate of forty nine point nine percent and Tina was at forty two percent. In addition, Kisara's health had taken a dive and her kidneys were beginning to fail completely. They had found a donor but Kisara was still being stubborn and refusing the donation.

In order to make up for not having an Initiator and in order to pick up the slack for Kisara so that they still made money, Rentaro had stopped having false skin cover his arm and leg, instead simply leaving them as exposed as his pants and coat would let them be. He had also had his arm modified to be able to form a knuckle duster trench knife on the fingers in reverse grip with the finger guards bladed. In addition, his pistol had been modified to have a finger guard of its own that was also sharpened and ran from the bottom of the grip to the bottom of the end of the barrel and was roughly two inches thick with a hole in it where the trigger was. He had become quite skilled at killing Gastrea alone and even civil officers of higher rank were very polite when talking to him, unlike the way it was before the war when everyone looked down on him for being young.

Rentaro stopped at the thirtieth Monolith and stopped. Several soldiers were patrolling the monolith and it looked to be just as solid as ever. But looks could be deceiving. The Gastrea had more than proven that. Rentaro watched the world beyond for a bit then turned and began to head back into the city. As he did, the one thing he knew would happen did. A pair of Stage I Spider Gastrea landed in front of Rentaro, one of them spraying half-liquid webbing at him as the other lunged. Rentaro snorted and leapt over the webbing, flipping and slamming an axe kick into the other Gastrea's back, blasting its torso into a dozen pieces. Then, he landed on his feet and darted forward, ducking under more webbing then standing and smashing his fist into the Gastrea, blasting it into pieces as well. Just as he did, a Bee Type Gastrea shot down out of the air at him and he snorted drawing his pistol and aiming at it.

"They never learn," Rentaro snorted firing a bullet into the Gastrea's face, dropping it to the ground and killing it.

He sighed and turned away from the Gastrea, walking away. He made his way to the outer district where the Cursed Children were located. After a bit, he arrived just as his phone rang.

"Hello?" Rentaro answered, watching the deserted streets.

"Hurry to the hospital," Enju's voice ordered. "It's Kisara."

Then, she hung up. Rentaro turned and sprinted through the streets until he reached the hospital, finding Enju waiting outside. He followed Enju to Kisara's room where Tina waited outside the closed door.

"The doctor's in there now," Tina stated. "We can't go in."

"What happened?" Rentaro asked just as the door opened.

"She's on life support," the doctor informed him. "She almost slipped. But she's stable. For now. She needs a donation. If she doesn't get one, she's going to die."

"I see," Rentaro nodded. "Is she awake?"

"We have her sedated," the doctor stated. "However, she gave me a message for you."

"What's that?" Rentaro asked.

"She said that her donation was up to you," the doctor said. "She told me to tell you that if you want her to, she'll let us give her a kidney."

Rentaro's eyes widened but she nodded.

"I don't suppose you already have a kidney," Rentaro asked.

"We do not," the doctor nodded.

"Can we get one?" Rentaro asked.

"Yes," the doctor nodded. "Unfortunately, it's not anywhere near here."

"Where?" Rentaro asked.

"It's in the Area just south of the Tokyo Area," the doctor stated.

"You make that sound close," Rentaro snorted. "It's a twenty miles to the outer district of that Area. Another three through there to the Safe Zone. The last time someone tried to make it there from here, they were massacred because of the Stage Four nest halfway there."

"I know," the doctor nodded. "But that is the only Area with a viable donor, and the only way for the donor organ to be usable is for it to be taken straight here rather than the long route through the other zones."

Rentaro nodded, staring at the ground then back up at the doctor.

"I'll go," Rentaro nodded.

"Not alone," Enju spoke up. "I'm going too."

"As am I," Tina agreed.

"And us," Tamaki Katagiri stated stepping around the corner. "If we need to go to another Area, you'll need backup."

Rentaro nodded then looked around. There weren't enough, especially since two were likely to die on the way and two were bad at following orders. But it would have to do. They didn't have time to find others.

"Alright," Rentaro nodded. "But I have to go see Sumire before we leave. I'll meet you all at the Thirty Second Monolith."

The others nodded and Rentaro left. When he arrived, Sumire was waiting at the door.

"It's complete," Sumire smiled. "It'll take exactly two days each, but the device is finally done."

Rentaro blinked then smiled widely. Then it faded.

"We're leaving now," Rentaro stated. "Kisara's getting a donor finally but it's in the Area to the south. So, can you keep Enju and Tina here?"

"No," Sumire sighed. "I'm sorry. They have to go. If not, they'll destroy the machine in their attempt to go after you. You should know that. Keep them safe. When you get back, I'll bring them here."

Rentaro nodded and left, going to meet the others.

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	2. Chapter 2

I do not own Black Bullet or any of the characters. Sorry for the extensive lapse in time since I did anything, I was at Marine Corps Boot Camp. Anyway, here goes nothing.

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Departure

Rentaro stepped up next to the monolith where a group of soldiers were shouting at Tamaki that he couldn't leave.

"We're leaving," Rentaro said flatly. "Nothing you say is going to change that. We have business to the south and don't have time to go the long way. Sorry but you'll just have to suck it up and do your jobs."

"But you'll get us all killed!" one of the soldiers shouted.

"Then you can kick my ass in the afterlife," Rentaro stated. "I know a few people already lining up to do it. Now, if there's nothing else. We're leaving."

"Fuck that!" the soldier shouted raising a gun and aiming at Rentaro. "You're under arrest for endangering the Tokyo Area."

"You want to arrest me?" Rentaro asked walking out of the Area a few meters. "Alright. Come get me."

Enju followed, Tina just behind her, and Tamaki and Yuzuki bringing up the rear, Tamaki already wearing his knuckles. The soldier stared at them incredulously as they began to head south before the soldiers all returned to their posts, all of their weapons ready now.

Rentaro stopped once they had entered the forest around the Tokyo area and Enju and Tina stopped as well.

"Tina, use your sniper only," Rentaro instructed. "You and Enju are not to engage Gastrea up close no matter what. If one reaches you, run. I don't care what's going on. Get back here and into the safe zone as fast as you can. Leave us. We'll be fine."

"You never told us our rates," Tina stated. "Are they really so bad?"

"Yes," Rentaro nodded. "They are. You're at forty two percent. Enju, you're at fifty nine point nine percent. If you are even around a gastrea, it may be enough to push it over the edge. If you come into direct contact, it's over."

"I'll be fine kicking ass," Enju promised.

"No!" Rentaro snapped. "You don't understand. Most start to change at forty eight percent! You're less than a tenth of a percent from dying! If you try to help, you die. I let you come because I know you won't stay behind. Do not fight. No matter what happens. Please. For me."

Enju nodded and Rentaro drew his pistol, turning south again and they began to walk, Tina taking up the rear with Enju in front of her. For a time, nothing attacked them and nothing even came close to attacking Tokyo, unsurprisingly. Everything was silent, except for their footsteps, and even those seemed muted. Finally, they reached a clearing and stopped. It had been hours and they had not seen even one Gastrea.

"Where are they?" Rentaro asked. "They should be swarming us already."

"Maybe it's better this way," Tamaki pointed out.

Just then, an unsettling shriek echoed out of the trees and they all spun, forming a tight circle facing outward with Enju in the center. Something flashed between the trees in front of Rentaro but before anyone could react, the air above them shimmered and blurred before an enormous spider appeared.

"Above!" Yuzuki shouted.

Rentaro's head snapped up as the spider began to descend. Enju crouched but before she could jump, Rentaro did, flipping and kicking the spider away from them. It's sheer size, rivaling a small house, made it impossible for him to send it far but he got it away enough for it to crash down without killing them. He flipped in mid air, falling toward it as it reared up, shrieking in rage and spewing acid at him. He rolled out of the way of the acid, redirecting himself toward the spider again. Before he reached it, a massive snake with purple and red skin shot out of the trees, swallowing him whole. The spider turned toward the others and Tamaki sprinted forward, chainsaw knuckles spinning to life. The spider leapt at him but hit a net set up by Yuzuki. Then, Tamaki shredded the spider, spinning to a stop and looking over at the snake as its body began to expand. Then, a massive sphere of blue fire exploded out of it, blasting the snake into several pieces and leaving Rentaro standing in its place, his sleeve shredded and his arm glowing and steaming.

"I hate snakes," Rentaro growled. "Come on. We should get going."

Everyone nodded and they left, continuing south. After a few minutes, they stopped when they found a massive glowing green venus flytrap in their path with vines winding and wrapping around the trees and ground around it.

"Tina?" Rentaro asked.

"I've never heard of a plant Gastrea before," Tina said shaking her head. "Should be safe."

Rentaro nodded, pulling out his pistol and starting forward. Just as he did, the vines all shot to life, reached for him at the same time as the fly trap opened, displaying rows of nasty-looking teeth. Rentaro jumped over the vines, firing at the plant but it had no effect. Tamaki carve a gash in the plant's side and green goo sprayed out of it. It shrieked in pain, a massive bundle of vines swiping through the air and smashing Rentaro into the ground. Just as he crashed down, vines shot out of the ground, driving themselves downward in a circle around the plant before it pushed itself out of the ground, a swarm of dozens of vines breaking free of the ground and reaching for them.

"Shit!" Rentaro shouted leaping backward from the vines and switching his pistol to the other hand and extending his knuckle blade.

Tina opened fire on the vines, trying to break through to the plant but with minimal success. Rentaro sprinted forward and slashed horizontally at the vines, severing several then leaping into the air as Tamaki tore into them. Vines shot up at Rentaro and he flipped over them then slashed them with his pistol's blade. As he fell, more shot up at him only to be caught by Yuzuki's webbing. Rentaro severed them as he landed then sprinted forward again as Tina pulled out a heavy machine gun and opened fire, the bullets tearing through the vines and shredding them.

"This isn't working!" Tina shouted as still more tentacles reached for them.

"Keep going!" Rentaro shouted, spinning and slashing several vines. "It can't have many more."

Just as he said this, the plant opened its mouth and hundreds of vines exploded out. Rentaro growled in frustration and sprinted forward, ducking under the initial wall of vines then slashing them and jumping over the next wave. Tamaki shredded into that one and Tina's machine gun shredded anything he missed. Finally, Rentaro flipped, landing on top of the plant and punched it, the force blasting it into the ground and spraying green goo out of its mouth. He jumped off as Tamaki carved into the plant and Tamaki leapt off just as vines burst out of it, spinning together into a sort of arm. The arm crashed down and the plant shrieked in rage as four more grew, all shorter than the last, turning the thing into a sort of alligator.

"Enough of this," Rentaro snarled. "Let's go Tamaki. Yuzuki, hold it still."

Yuzuki nodded, binding it with webbing quickly as Tamaki and Rentaro both leapt into the air over the plant thing. It roared, breaking free and looking up at them. Tina shot it in the abdomen before it could attack them and it fell to its feet again just in time for Rentaro and Tamaki to crash into it's back, flattening it. Finally it died and the two of them stood as the others made their way over.

"Done," Rentaro sighed. "I hate Gastrea. How far to the nest?"

"Roughly three miles," Tina estimated. "Another fifteen past it to the Area we're trying to get to."

Rentaro nodded and they continued walking, moving a bit slower this time to rest as much as they could before the nest.

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	3. Chapter 3

I do not own Black Bullet or any of the characters.

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Nesting

Rentaro stopped on top of the cliff, standing beside Tina who was watching the nest through her sniper rifle.

"I don't see anything," Tina reported. "They could all be underground. Or it could be a trap."

"And if they're underground?" Rentaro asked.

"We may be capable of sneaking past, but we don't know the Gastrea's capabilities," Tina stated. "The most likely scenario is that we will be detected. We do not have enough time to go around though. Our options are limited."

"I don't suppose I could get you and Enju to go home," Rentaro tried.

"No," Tina said flatly. "However, we will go around the nest. We will meet you on the far side. I'll cover you from a distance. I'll also send my new automated drones with you. They're armed with fifty cals and Mark Nineteens."

"Thank you," Rentaro smiled. "Take one with you. You need protection."

Tina nodded and pressed a button on a small black box. A moment later, five drones arrived, three armed with fifty caliber machineguns and two with Mark Nineteens. Tina signalled Enju to follow then left with a drone, Enju catching up quickly. Then, Rentaro went down to the others and they headed toward the nest. As they walked, Tamaki turned to look questioningly at Rentaro, seeing if he had noticed. Rentaro nodded. He had noticed. The forest around them was silent. All Gastrea and any normal animals that may have been around them had fallen silent. The wind had also stopped, creating a silence so complete that it seemed as though every step they took was deafeningly amplified. Rentaro could hear his heart beat, could hear his lungs expand and contract as he breathed. He could hear his blood flowing through his veins and his muscels flexing and contracting as he moved. He suddenly stopped. They were at the edge of the nest now, and as they had moved closer, the disorienting volume of his internal functios, and equally disorienting lqck of any other sound had simply increased. It wasn't natural. It wasn't adrenaline, fear, or nerves. It was noise suppression.

"Stop," Rentaro whispered, his voice lost to him as he was assaulted by the sound of him exhaling, his jaw moving, his tongue moving, and air moving against his vocal cords, making them vibrate.

"I noticed too," Tamaki replied, wincing as the same effect gave him the sam headache Rentaro was fighting. "This will be bad."

Rentaro nodded just as his head went fuzzy as noises that seemed to be passing through water hit his ears. There was a near constant string of muted pops, alternating from one side to the other and back again. After a moment a string of deeper pops began as well at a slightly slower rate and then a slightly louder and much deeper string began at the same rate as the second string but a half second off.

Rentaro looked away from the others in the direction of the noises. The drones. They were firing. He looked where they were firing and a tiny bit of sense returned, enough for the utter chaos before him to make sense. There were explosions and sprays of multicolored blood everywhere. Pieces of Gastrea flew in every direction and yet still more swarmed out of holes now pock-marking the nest. Rentaro could see stage I Gastrea, stage II, and even a couple of stage III. But so far, there were no stage IV.

Rentaro drew his pistol, firing at the Gastrea, his brain swirling as his pistol fired silently and what seemed like in slow motion. Everything seemed to be happening in slow motion, yet so very fast as well. After what he could swear was only five shots, his pistol was empty, but he knew the magazine had been full. He reloaded with his last magazine, but that couldn't be right. He had had twelve before. Before he could fire, a Gastrea crashed into his back, slamming him into the ground and then bright blue blood splattered across the ground. Tamaki pulled Rentaro up and a snake lunged at them both. Its bead exploded from a sniper round and Rentaro spun, his foot flashing up and kicking a spider out of the air, blasting it into pieces.

Then, a massive Gastrea with black skin, glowing blue spots over its body, and gill-like slits that opened and closed every few seconds appeared, a massive tentacle swiping through the air, destroying three of the four drones. Rentaro turned toward the Gastrea and it smashed him backward into Tamaki. They crashed to the ground and Yuzuki rushed over, trying to speak but the Gastrea's ability seemed to have rendered Rentaro's hearing useless, as he could not hear what she said. He tried to stand and a wave of nausea hit him, making him fall to his knees and vomit. Tamaki tried to stand but had a similar result. A moment later, Yuzuki seemed to lose her balance and fell.

Rentaro raised his pistol but before he could fire, a sniper bullet punched a hole in the side of the Gastrea's head. It shrieked in pain, the sound easily registering in Rentaro's muted ears as the last drone and Tina's both flew to opposite sides, opening fire. It shrieked again, smashing both drones. Then, Rentaro heard Enju scream, even through the Gastrea's ability. He looked sideways, seeing Enju and Tina run out of the trees into the nest, which was crowded with Gastrea that were no longer being held back by drones. Gastrea followed them, attempting to catch the two agile children. Just as the Gastrea began to close in, a familiar cursed child wielding a pair of katana landed in front of them, spinning and shredding them. Then, it turned, leaping at the other low-level Gastrea moving to attack Tina and Enju. As the girl shredded them, the massive black Gastrea turned toward Rentaro again. A tentacle reached toward him, but before it could grab him, it was suddenly blasted by some invisible force that sent the entire Gastrea sailing into the horde behind it.

Instantly, the deafening effect of the Gastrea vanished, along with the nausea and Rentaro stood, now aware of the chorus of screams the Gastrea were releasing. Enju and Tina stopped beside him, glaring at a man dressed in a maroon suit with a white mask.

"Kagetane," Rentaro snarled.

"Hello again Rentaro," Kagetane greeted. "It's been some time. I was passing by and saw my favorite opponent was in danger. So I decided we would help. Shall we?"

"Go fuck yourself," Rentaro snarled. "I don't need your help."

"Is that right?" Kagetane sneered. "Very well. Good luck protecting those children you're so fond of."

He turned to leave but Rentaro grabbed his arm.

"Help me kill the stage IV, then leave," Rentaro snarled.

Kagetane's yellow eyes seemed to glow and Rentaro somehow knew that his facial expression matched his mask. Then, Kagetane bowed. He turned, sprinting at the Gastrea and blasting into them. Rentaro and Tamaki followed, wiping out Gastrea almost as fast as Kagetane. Finally, the only one left was the stage IV. Rentaro turned on it, blue flames shooting out of his arm, propelling him toward it until his fist crashed into its side at the same time as Kagetane's Endless Scream blasted through from the other side, only narrowly missing Rentaro

Rentaro landed off to one side as the Gastrea crashed down and looked over at Kagetane, who was standing beside Kohina. Kagetane bowed, mask never turning away from Rentaro. Then, he turned and left. Kohina followed, also not taking her eyes off Rentaro.

Rentaro sighed as Enju and Tina walked over, Tamaki and Yuzuki following.

"I don't like them," Enju stated.

"Agreed," Rentaro stated. "Now, we should leave before the other four stage IV's that live here show up."

Tina nodded and they turned, hurrying away from the nest. After they were a ways into the trees, they slowed, watching the trees carefully. Rentaro pulled out his magazine and checked it and his pistol, as well as his usual conceled magazine places. He had exactly five shots to get him the rest of the way to the southern safe zone. Maybe back, if the security force of that zone didn't accept him as readily as he was hoping.

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